Star-like microgels vs star polymers: similarities and differences

TL;DR

This study uses simulations to compare star-like microgels and star polymers, revealing their similar ultrasoft behavior and potential for high-concentration applications.

Contribution

It establishes a theoretical analogy between star-like microgels and star polymers through detailed simulation analysis.

Findings

Effective potential is Gaussian for star-like microgels, unlike standard microgels.

Gyration and hydrodynamic radii ratios show qualitative agreement with star polymers.

Star-like microgels are significantly softer than standard microgels, similar to star polymers.

Abstract

Star-like microgels have recently emerged as a promising class of thermoresponsive soft colloids, that have an internal architecture similar to that of star polymers. Here, we perform extensive monomer-resolved simulations to theoretically establish this analogy. First, we characterize the effective potential between star-like microgels, finding that it is Gaussian for an extended range of distances, in stark contrast to the Hertzian-like one of standard microgels, but almost identical to that of star polymers with a core partially covered by chains. Next, we investigate the ratio between gyration and hydrodynamic radii across the volume-phase transition, showing qualitative agreement with both star polymers and experimental data. Finally, we estimate the bulk modulus, finding star-like microgels significantly softer than standard microgels and comparable to star polymers. The present work thus demonstrates that star-like microgels behave as ultrasoft particles, akin to star polymers, paving the way for their exploration at high concentrations.